This type of cooling device not only cools an internal combustion engine by circulating coolant between a fluid passage formed in the engine and a radiator, but also supplies the coolant to a heater circulation flow path including a heater core for heating. Further, in recent years, a cooling device has been devised that uses the coolant from the engine for an exhaust gas recirculation (EGR) cooler and a throttle body.
Thus, to circulate or supply the coolant to each part as described above, it becomes necessary to use branch pipes to individually connect pipes to each other. Thus, piping in an engine room becomes complicated, and as a result, this causes a problem to occur of lowering maintainability of the engine.
To simplify connection of the pipes, in the following prior art literature disclose that a coolant passage device is directly connected to a coolant discharge port of the engine, accommodates a water temperature sensor, for example, in the device, and in which device connection ports of the pipes are aggregated.